1. Field of the Invention
This invention relates to an apparatus for filling containers with a particular weight of liquid and, more particularly, to a subsurface filling apparatus having a pneumatically-controlled lance assembly.
2. Description of the Related Art
A number of types of equipment have been designed for filling large containers. With liquids susceptible to foaming, the lower discharge end of the lance that is used for filling the container is often placed near the bottom of the container. The drum filling apparatus disclosed by Reeves, Jr. et al. (U.S. Pat. No. 4,703,780) has such a subsurface lance that utilizes a weight-responsive apparatus that automatically raises the filling lance during the filling operation so that only a small portion of the lance remains below the liquid surface. This patent and all other cited patents are hereby incorporated by reference. This apparatus has two fill rates (an initial fast rate followed by a final dribble fill) with which the rate of rise of the lance is coordinated. One signal generator causes a lowering movement of the lance, and a second signal generator operating in cooperation with the weight-responsive apparatus causes the upward lance movement. This invention does not disclose a fully pneumatic subsurface filler and thus presents potential explosion problems with low TLV gases (OSHA's threshold limit values).
An earlier patent of Kennedy et al. (U.S. Pat. No. 4,337,802) also has an automatically withdrawn lance while the discharge end of the lance remains beneath the surface of the liquid. A first signal generator actuates downward movement of the lance. The second signal generator is actuated by the downward movement of the lance. A delay mechanism, actuatable by the second signal generator causes the fast fill, and a third signal generator, actuated by the rise of the lance to a predetermined height, causes the lance to stop movement. Initiation of the termination of the liquid flow and upward movement of the lance are actuated by a second control signal form the second signal generator when a predetermined weight is reached. Again, this filler is not fully pneumatic. Furthermore, it has many machined parts, parts that are potentially exposed to corrosive fumes, and parts that are relatively inaccessible. These features increase the cost of the filler, and make it expensive and/or difficult to use and to maintain.
Another problem found in subsurface filling is that of drip collection. To solve this problem, the apparatus disclosed in U.S. Pat. No. 4,337,802 has a drip collection assembly consisting of a movable drip pan, a fixed drip outlet tray and a drainage hose. The movement occurs by a piston-cylinder assembly controlled by pneumatic circuitry. This apparatus also has a wiper ring assembly through which the lance is withdrawn and which serves to remove the liquid from the surface of the lance.
Noxious vapors are often a problem with subsurface fillers. Many of the exhaust systems of subsurface fillers are not designed for efficient removal of large quantities of harmful liquid vapors, and a dangerous vapor buildup may occur. The vapors and corrosive liquids may also harm the parts of the filler. Thus, these parts require considerable maintenance time and replacement parts.
Subsurface fillers generally have one or more electronic controls. This presents a problem when explosive vapors are ignited by an electronic signal. To avoid this problem, explosion-proof fillers must be constructed for use with explosive vapors, which increases the cost of the fillers.
Because subsurface fillers are generally constructed of many machined parts, they are expensive to construct and to buy even if not constructed to be explosion-proof. It is therefore an object of this invention to provide a subsurface filler that has few machined parts and is relatively inexpensive.
It is a further object of this invention to provide a subsurface filler that enables accurate filling of a container.
It is a further object of this invention to provide a subsurface filler that has easily controlled lance movement while the discharge end of the lance remains beneath the surface of the liquid.
It is another object of this invention to provide a subsurface filler that is entirely pneumatically controlled.
It is another object of this invention to provide a subsurface filler that has a pneumatically activated drip tray.
It is a further object of this invention to provide a subsurface filler that has an efficient exhaust system for noxious gases.
It is a further object of this invention to provide a subsurface filler that requires little maintenance and has a long useful life.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.